Improvement in manufacture of soaps



UNITED STATES PATENT OFFICE.

FRIEDRIGHKNAPP, OF BRAUNSGHVVEIG, GERMANY.'

IMPROVEMENT IN MANUFACTURE OF SOAPS.

Specification forming part of Letters Patent No. 221,072, dated October28, 1879; application filed May 13, 1878.

' nary soap through the agency of a solution of the special basicsulphate of iron, Letters Patent for which were granted to me July 24,1877, said Letters Patent being numbered 193,521.

For the better understanding of this my present invention, I willbriefly describe the process of making the aforesaid basic sulphate ofiron, and its properties which distinguish it from other basic sulphatesof iron.

The said special basic sulphate of iron is made asfollows: To a boilingsolution of proto-sulphate of iron (green vitriol) is added as muchnitric acid as will thoroughly oxidize the salt contained in the saidsolution. When the 'effervescence which ensues upon the addition of thenitric acid has subsided, the operation is reversed-that is to say,sulphate of protoxide of iron is added to the solution till saidsolution assumes a sirupy consistence, and acquires a yellow-red color.The said sirupy consistence of the solution of the. said salt, theyellow'red color, and the appearance of an orange-red transparentvarnish, when the said salt is solidified by slow evaporation of thesolution, are peculiar characteristics of the said basic sulphate madein the manner described. I

The color of the solidified salt is much lighter than that of the basicsulphate of iron hitherto known, and it possesses the property ofresisting the decomposing action of heat while in a state of solution.It is capable of being boiled in solutions of the strength of from 30 to40 Baum without decomposition unlike the before-known basic sulphate of,iron, which decomposes when boiled in aqueous solution. The said basicsulphate of iron has, moreover, the property of .being eopiously takenup by the skins of animals, in which it produces remarkable chan ges,rendering said salt an important reagent-in the manufacture of leather.

I make the iron soap which forms the subject of the present applicationby precipitatin g it from a solution of ordinary soap through the agencyof a solution of the said sulphate, which decomposes the solution ofordinary soap in proportion to the amount added until the whole of thefatty acids have been separated from the alkaline base or bases.

It will -be seen that so much of the said basic sulphate is added to thesoap solution as is required to form the iron soap; and it is evidentthat the proportions cannot be positively fixed, inasmuch as they differaccording to the strength of the soap solution. I would here state,however, that for one hundred parts of the soap forming the presentinvention, the following proportions will be found satisfactory: 9.51parts of the mixed sulphate, and 90.49 parts of the fatty acids ofordinary soap.

The iron soap thus produced is especially designed for use in tanningpurposes, and it will be copiously taken up by the skins of animals inwhich it produces, as before stated, remarkable changes, rendering it animportant agent in the manufacture of leather.

Having thus described my invention, what 1 claim, and desire to secureby Letters Patent, is-

The iron soap made from a solution of ordinary soap by the use of asolution of the herein-described basic sulphate of iron, substantiallyas and for the purpose specified.

In testimony that I claim the foregoing I have hereunto set my hand.

'DR. FRIED. KNAPP.

